A problem with a telephone line that prevents a customer from receiving or making calls is upsetting to both the customer and the telecommunications company. The file Phone contains samples of 20 problems reported to two different offices of a telecommunications company and the time to clear these problems (in minutes) from the customers’ lines.

a. At the 0.05 level of significance, is there evidence of a difference in the variability of the time to clear problems between the two central offices?

b. Determine the p value in (a) and interpret its meaning.

c. What assumption do you need to make in (a) about the two populations in order to justify your use of the F test?

d. Based on the results of (a) and (b), which t test defined in Section 10.1 should you use to compare the mean time to clear problems in the two central offices?